RFID systems include different arrangements of antennas, which may transmit an RF carrier wave as well as receive backscattered radio waves through their antennas. Some conventional products implement one dimensional antenna arrays (linear antenna arrays) to achieve transmittal of narrow, directional transmissions, e.g., for far field applications. However, to achieve such directional functionality, in addition to reducing parasitic side and back radiation, conventional products sacrifice uniformity and ultimately create an uneven distribution of energy short distances from radiating elements, e.g., less than one wavelength of the radiated field and/or less than a linear dimension of the antenna array. This is particularly apparent for near and/or medium electromagnetic field applications. For instance, the field produced by RFID applications having conventional linear array antennas may have a difference of about 20-30 dB between opposite sides thereof. For examples of such conventional disadvantages, see any of the following U.S. Pat. No. 3,806,946 entitled “Travelling wave chain antenna”, U.S. Pat. No. 4,180,817 entitled “Serially connected microstrip antenna array”, U.S. Pat. No. 4,521,781 entitled “Phase scanned microstrip array antenna”, U.S. Pat. No. 5,422,649 entitled “Parallel and series FED microstrip array with high efficiency and low cross polarization”, U.S. Pat. No. 6,424,298 entitled “Microstrip array antenna”, U.S. Pat. No. 7,095,384 entitled “Array antenna”, U.S. Pat. No. 7,109,929 entitled “TM microstrip antenna”, U.S. Pat. No. 7,518,554 entitled “Antenna arrays and methods of making the same”, U.S. Pat. No. 7,525,487 entitled “RFID Shelf Antennas”, U.S. Pat. No. 7,554,491 entitled “Low Profile Distributed Antenna”, U.S. Pat. No. 7,733,280 entitled “Antenna system”, U.S. Pat. No. 8,058,998 entitled “Elongated twin feed line RFID antenna with distributed radiation perturbations”, U.S. Pat. No. 8,078,215 entitled “Waveguide-based wireless distribution system and method of operation”, U.S. Pat. No. 8,193,990 entitled “Microstrip array antenna”, U.S. Pat. No. 8,289,163 entitled “Signal line structure for a radio-frequency identification system”, and D617318 entitled “RFID antenna.”
In an attempt to overcome such disadvantages of conventional linear antenna arrays, other conventional products have implemented parallel configurations, which essentially combine multiple radiating elements of linear antenna arrays in parallel using power dividers or transmission lines transformers. Although this parallel design may improve the uneven distribution of energy found in the conventional linear antenna array, they introduce additional problems. Combining multiple radiating elements in a linear antenna array requires extensive cabling, thereby undesirably increasing power consumption, as well as the cost of fabrication and/or upkeep.